Scanning tunneling spectroscopy of Bi2Sr2CuO6+δ:: New evidence for the common origin of the pseudogap and superconductivity

Using scanning tunneling spectroscopy, we investigated the temperature dependence of the quasiparticle density of states of overdoped Bi2Sr2CuO6+delta between 275 mK and 82 K. Below T-c = 10 K, the spectra show a gap with well-defined coherence peaks at +/- Delta (p) similar or equal to 12 meV, which disappear at T-c. Above T,, the spectra display a clear pseudogap of the same magnitude, gradually filling up and vanishing at T* similar or equal to 68 K The comparison with Bi2Sr2CaCu2O8+delta demonstrates that the pseudogap and the superconducting gap scale with each other, providing strong evidence that they have a common origin.